PM70270: A LOWER BUFFER HIT RATIO OR MORE SYNCHRONOUS I/O IF VPSEQT IS SET TO A SMALL VALUE

A fix is available

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APAR status

Closed as program error.

Error description

When a random Getpage buffer miss resulted in DB2 stealing a
buffer from the sequential LRU chain, DB2 did not remove the
buffer from the sequential LRU chain when it should. This meant
that random pages were more likely constricted by VPSEQT.
Therefore in some cases, recently used buffers were stolen more
quickly than less recently used buffers, resulting in a a lower
buffer hit ratio or more synchronous I/O. The impact of this
problem is relatively small if the default VPSEQT value of 80%
is used, but the impact is likely to be large if VPSEQT is set